Prior to the advent of the rotary cutting tools the interaction of all the previously known tools with the workpiece was accompanied by a sliding friction between the produced chips and the front face of the tool and by a sliding friction between its back surface and the surface of cutting.
It is also common knowledge that the velocity of the relative sliding between the cutting tool and the surface being cut determines to a considerable extent the power expenditures for the process of cutting, the durability of the cutting tool, quality and precision of the machined surface. A reduction in the velocity of relative sliding can be achieved by partly substituting the sliding friction between the tool and the workpiece for rolling motion. This principle has been pursued in devising the rotary cutting tools wherein the cutting portion in the form of a body of revolution, for example a tapered cup, rotates in the course of cutting around it geometrical axis due to interaction with the workpiece or, in some cases, is rotated by a special drive. This permits the life of the rotary cutting tools to be increased many times as compared with the prior art tools, at the same time improving the precision, quality and efficiency of machining.
Alongside with the positive characteristics of the rotary cutting tools, their common disadvantage lies in an insufficient vibration resistance and stiffness which is attributable to the provision in their construction of a rotary element mounted on bearings in the tool body. Therefore, if we consider the stiffness of the entire system "machine tool-jig-tool-workpiece", most often the tool, i.e. the rotary cutting tool will be the weakest link in the process of rotary cutting. Accordingly, the most efficient method of raising the resistance to vibration of the tool and, consequently, its efficiency, precision and quality of the machined surfaces is the perfecting of the design of the rotary cutting tools which raises their stiffness and vibration resistance without substantial increase in dimensions.
Known in the prior art is, for example, a rotary cutting tool whose rotating element is constituted by a spindle which carries a dish-shaped cutting element and is mounted in the tool body on bearing supports. The cantilevered mounting of the cutting element with respect to the bearing supports of the spindle causes the latter to be bent in the course of cutting which, in combination with the contact deformations of the bearings, produces the pressing-away forces which push the tool from the surface of the workpiece.
The magnitude of the pressing-away force varies considerably with the different cutting forces which may change under the effect of varying machining allowances, variations in the physical and mechanical properties of the material being machined, etc. This brings about considerable difficulties in ensuring the high precision of dimensions and shape of the machined surfaces. The variations in the pressing-away force increase the intensity of vibrations during cutting, impair the micro- and macrogeometry of the machined surface. In large-scale production where the possibility of test passes on machine tools is nonexistent, the non-uniformity of the pressing-away forces acting on the rotary cutting tools due to their low stiffness is accompanied by a considerable increase in the spread of dimensions of the workpieces, which decreases the machining accuracy.